Charge forming device



March 1945- M; E. CHANDLER CHARGEFORMING DEVICE Original Filed March 31, 1941 o o Y -t Patented Mar. 2?, i945,

, UNITED STATES omen roamojnavrca Milton E. Chandler, New Britain, com, assignor,.

to Chandler-Evans Corporation; South Meriden,

Conn., aoorporation of Delaware continuati n of application Serial No. 386,04G, March'31, 1941. This application February 3, 1943, Serial No. 474,515 g 6 Claims;

This application is a continuation of my application Serial No. 386,046, filed March 31, 1941.

This invention relates to charge forming devices, and while not limited thereto it has pargiicular reference to carburetors for aircraft ennes.

One of the objects of the invention is to pro-.

vide an improved fuel and aiflproportioning device for an internal combustion engine.

Another object is to provide an improved device applicable to aircraft carburetors for supplying fuel to the manifold in a manner to compensate for fluctuations in the weight and other characteristics of the air supplied to the engine under different operating conditions.

In the accompanying drawing:

Fig. 1 is a somewhat diagrammatic sectional view showing an aircraft carburetor provided with a charge forming device embodying my invention,

and

Fig. 2 is an enlarged view of a portion of the regulator valve mechanism shown in Fig. 1.

In the drawing, a carburetor body or casing is shown at I, the same having an air passage 2 extending therethrough provided at one end with an enlarged inlet or scoop 3 and at the opposite end having a portion 4 adapted to communicate with an adjacent part inot shown) of the manifold structure. passage adjacent the end portion 4 is a fuel supply jet or nozzle 5, and upstream from nozzle 5 is a pair of throttle bars or flaps 6 adapted to be turned by means of shafts 1 fixed thereto,

said shafts extending completely across the passage. In the'passage somewhat below the scoopportion 3 (Fig. 1) is a restricted throat or Venturi portion 8. A control device located at the right-.

hand side of the carburetor (Fig. 1), and gener-. ally indicated at 9, is actuated by variation in the pressure differentials between the scoop 3 and the throat 8'in a manner to be hereinafter described.

, The liquid fuel supplied is derived from a fuel tank l delivering fuel through a pipe-ii to a fuel pump II of the constant pressure type, whence fuel is pumped through a pipe 13 to a vapor trap-andfilten device l4, and 'a retu-m pipe l leads from device M back to the tank Ill in order 'to return to the tank vapor rising to the upper partof device 14. The fuel passing from device It moves through a pipe 16 to a, regulating device I1, and

from the device I! the greater part of the fuel supplied to said device passes upwardly through a pipe l8 to a manually adjustable fuel control- Located in the main air to the nozzle or iet 5 ling valve l9 having parallel fixed orifices 20 and a parallel spring-loaded power Jet 2 i. From the valve I9, the fuel passes through a pipe 22 to a main metering orifice or restriction 23, which 5 in this instance is located in the left-hand wall structure (Fig. 1) of the carburetor part of the manifold... From orifice 23 fuel passes throu h a valve 24 to'nozzle i by way of a passage 25 controlled by a manually operable'valve 2t connected to the throttle bars to be operated concurrently therewith. The valve 26 is a pressure control valve-serving to maintain a minimum pressure in the conduit downstream of the metering restriction. At the side of valve 26 which is upstream, passage is provided with a small vent or bleed 25 into the main air passage.

* Connection from valve 2t to one of the "throttle bar shafts I is made by ans such as an arm 2'lrigid with valve 26 connected. by a link 2 20 to an arm 29 rigid with the said shaft l.

, The constant pressure pump l2 illustrated in the drawing includes inits structure a by-pass valve 30' connected to and actuated from a diaphragm 3|, which is subject on the lower side '25 (Eig. 1) to pump discharge pressure inasmuch as,

the-fuel passes to the under side of-the'diaphragm through ports 32 in valve 86). On the upper side of the diaphragm 8i a coilspring J3 biases the diaphragm to hold the valve 30 in 30 thelowermost, closed position shown in Fig. 1.

Upon the building up of excess pressure in the conduit on the discharge side of the pump, be-

, yond a predetermined degree, the valve 30 will 1 be moved upwardly to unseat it andto enable passage of fuel back tothe pump inlet, By this arrangement the pump is caused to maintain a substantiallyconstant fuel pressure in the portion I; of the fuel conduit.

-Now referring to the preferred structure of the regulating device I], it will be noted that this device comprises a body or casing 34 at the upper part and a body or casing 35 at the lower part. 4 The 34 contains atfone side a passage '38 leading "into it from pipe i8, and at the opposite side it is provided with a passage 81 providing an outlet to pipe l8. Casing part 35 includes separate sections 38 and 39 between which is clamped a diaphragm i0. Attached to and extending through this diaphragm is a spindle 4| of a valve 42 operating in the upper casing part 34-. The valve it operates within a fixed sleeve 43 providing a valve chamber, and

The valve 42 is a hollow sleeve valve carrying at its upper end (Fig. 2) an external conical seat 45 and carrying at its lower end a similar seat 46. The seat 45 is adapted to co-act with a fixed ring 41 carried at the interior of sleeve 43, and the conical seat 46 is adapted to cooperate with a ring-like extension. 48 of member 43. Above the extension 48, the sleeve 43 is provided with radial ports 49. A pressure chamber 58 is provided above the diaphragm 40, this chamber be ing in communication with passage 31 and being in communication with the chamber 44 by way of ports 5| around the valve stem and by way of the radial ports 49 previously mentioned.

A restricted communication passage from the chamber 58 above the'diaphragm to a chamber 52 below the diaphragm is provided in a suitable manner, as by having small ports 53 and 54 in '58 having a nicked head 59 accessible at the exterior of the casing. By turning the screw in one direction the spring may be subjected to additlonal compression, and by turning it in the opposite direction the compression may be lessened, thereby decreasing its valve-opening tendency.

The chamber 52 at the lower side of the diaphragm is connected with. the control device 9 previously mentioned by way of a pipe 6|) providing a restricted branch connection or branch conduit from the main conduit, and this branch conduit carries a small portion of the fuel supplied to the regulating device l1, namely, that portion which passes from the upper side of the diaphragm to. the lower side by way of the connection 53, 55, 54. By properly .proportioning the passage from one side of the diaphragm to the other; the proper relative amount of fuel can be caused to flow to the branch connection.

In general the operation ofthe regulating device I1 is as follows:

Fuel passing into inlet passage 36 reaches chamber 44, and thence passes inwardly by radial ports 49 to the interior of sleeve 48, and thence by axial ports 5| to the chamber above the diaphragm, and the greater part of the fuel passes from this chamber by way of passage 31. Arelatively small portion of the fuel passes, however, to the chamber below the diaphragm, as above explained, and thence to branch pipe or conduit 60. In Fig. 2 the-valve 42 is shown in the open pos tion. However, when the fuel pressure above the diaphragm reaches a predetermined degree,

.the diaphragm has its central portion moved downwardly'sufliciently to close. the valve and prevent further fuel from reaching chamber 50. When the valve is in the closed position the seat 45 engages member 41, and the seat 46 engages member 48. Owing to the open formation of the valve and the provision of its external terminal seats on opposite sides of the ring 41, it is not, when in open position, subject to prejudicial fluctuations or sudden. movements, as there i a substantial balanc ng of the forces acting on it in opposite directions.

as'rassc The control device 9, which is afiected by changes in the amount of air entering the main air passage, is preferably of the diaphragm type, and comprises a diaphragm 6| clamped between an inner member 62 and an outer member 63 so as to provide a chamber 64 at the left-hand side of the diaphragm and a chamber 65 at the righthand side. Secured to the central portion of the diaphragm within the chamber 64 is a valve body 66, which valve body, as hereinafter described, is a part of a pilot valve mechanism which controls the venting of fuel from the branch conduit of which the pipe 68 is a part, and thereby controls the position of the valve 42.

From the venturi or throat portion 8 of the main passage a controlling air-pressure connection is made in a suitable manner to the chamber 64, and in the particular form shown this includes a passage 61 at the throat having small suction openings 68., From passage 61 a passage 69 is extended to an annular passage 10, and passage I0 communicates with a short passage ll leading to chamber 64, and annular passage 10 also leads to a restricted passage or bleed 12 having a restricted end portion 13 leading into the chamber 65.

In the scoop portion 3 of the main air passage are small pressure inlets 14 to a passage 15 extending around the air passage. This passage 15 communicates with a chamber 16 in the righthand wall structure of the carburetor, and in the chamber 16 is an anercid device 11 of usual structure around which air can circulate, havin its interior passage 18 controlled by a valve 18 and in communication with a passage 88 leading upwardly and then laterally and then downwardly, as shown in Fig. 1,'s0 as to communicate with the chamber 65 at the right-hand side of the diaphragm 6|. A temperature bulb 8| associated with the aneroid device 'I'I projects into the main air passage of the carburetor somewhat upstream of the throttle bars.

Reverting to the valve 66 carried by diaphragm 6|, it will be seen that this valveis adapted to make contact at its left-hand end with and to be controlled by a diaphragm 82, which is marginally clamped between suitable members in such a I manner that said diaphragm 82 provides a portion of the left-hand wall of chamber 64. A biasing spring 83, which may be a coil spring and which is located in chamber 65, acts on diaphragm -6l so as normally to hold valve 66 against diaphragm 82, and diaphragm 82 in turn against a valve seat 84 controlling a passage 85, which is adapted to vent the branch fuel pipe 60 in a suitable manner. Spring 83 is a compression spring,

and the degree of its compression can be controlled by suitable means such as an exteriorly accessible adjusting screw 86 connected to a cup 81 receiving the right-hand end of the spring.

The valve seat 84 is at the exit of a small chamber 88 at the left-hand side of the secondary diaphragm 82. The pipe 60 is in communication with a passage 89 in the carburetor wall, which passage leads to the small chamber 88, and if fuel can pass through chamber 88 and valve seat 84 it will flow into the passage previously mentioned.

In the particular form shown the passage 85 is arranged to conduct any vented fuel to the main passage of the carburetor upstream of the throttles, and for this purpose passage 85 is connected to a lateral passage 90 communicating with a small tube 9| which projects into the main passage to a slight extent.

conditions.

In theoperation of the device fuel is supplied at constant pressure by pump I 2 to the regulating device l1, from which fuel passes to-the main metering restriction 23 in the main conduit. A certain amount of the fuel passing to the regulating device flows to the under side of the diaphragm or movable wall in a manner previously described, so

as to provide a relatively reduced pressure on the movable wall and its valve. As above noted, the fuel at the under side of the diaphragm is free to flow. through the branch connection or conduit 60, 89, 88, 85, 90, 9|, provided valve 86 is in a position to permit this. The spring 56 nore mally holds the movable metering or regulating valve in the open position.

Assuming that the engine is in operation at a relatively high s'peedin which case there will be a considerable pressure differential between the scoop and throat portions of the air passage, and the throttles are moved toward the closed position so as to reduce the speed, the pressure differential between scoop and throat will be reduced, and assuming that when-the engine is at high speed the valve 66 is closed, the change of The speed will be effective to open the valve. opening, of this valve will then be effective to enable fuel to pass freely out of the branch connection, which will reduce the pressure in the branch connection, reducing the'pressure below the dia-- phragm of the regulator' device 11, and thereby causing the fuel pressure above the diaphragm to move the valve toward the closed position so assists the spring throughout the range of engine operation. The fuel at the under part of the diaphragm can pass out of the casing of the regulating device owing to the provision of the discharge therefrom provided in this particular case by the pipe 60, and by building up the pressure of the discharge through the closing of the discharge or vent connection, as above described, the position of the metering valve'can be changed in accordance with the varying air supply to the engine. The metering valve is, of course, moved in the opening direction at any point in the range of engine operation when the pressure beneath the diaphragm is increased to a point where it, conjointly with the action of the spring 56, will overcome the pressure onthe upper side of the diaphragm.

as to permit less fuel to pass to the restriction 23.

Thus the amount ,of fuel being supplied is reduced, as is desirable under the condition mentioned.

- Thus it willbeseen that, as the air supply to the manifold is decreased, the fuel supply to the manifold (or to some other desired location) is correspondingly decreased. In the operation of ventingsurplus fuel from the branch connection,

this relatively small quantity of fuel may be carried into the manifold, as above described, al-- though this is merely by way of example, and

other arrangements can be provided in that respect. Assuming now that the speed of the engine is again increased, the'resulting increase of air -regulating valve structure is employed, and a simple air-supply-controlled valve device, and if repairs to one of these devices is necessary, they can be effected without disturbing the other device, and the means of connection between these devices is very simple and inexpensive, and it is possible to place the fuel-regulating valve and the .fuel-vent-controlling valve at various locations relatively to each other and to the carburetor body, so that the' apparatus can be assembled and installed to a large degree in accordance with the dictates of convenience, saving of space, etc. The apparatus can be used to great advantage in various fuel and air proportioning systems in which a constant pressure fuel pump i employed, whether or not the metered fuel is supplied to a manifold or the like. Also, it will be evident that certain components of the apparatus, such pressure differential in the air passage will causef the valve 66 to be closed again, thereby closing the branch connection intermediate of its ends and causing pressure to be built, up again in that portion of the branch connection which is on the sure builds up-in the branch connection itcauses pressure tohe built up under the diaphragm of the as the fuel supply regulating device and the aircontrolled vent valve for the fuel, are of improved structure and are well adapted for use in av sy tern such as described. I

-Whi1e only one embodiment of the invention is shown and described, it will be apparent that the invention is susceptible of numerous embodiments j and that various changes in the organization of fuel-receiving side of the valve seat 84. As pressupplying more fuel, as is desirable under these' It is also to be understood that with the throttle in any given setting, during engine operation, the

valve-66 will have movement from time to time as conditions of air pressure, air density, temperature, etc. vary, so as to cause corresponding compensating movements of the meterin valve.

It is'important to note that thespring 5B of the regulating device has the function of acting operation, said spring throughout said range biasing said valve to an open'position. The pressure of the fuel entering the regulating valve casing opposes the action of this spring throughout the range of engine operation, and similarly the pressure of the fuel at the under side of the diaphragm, exerting less than the upper pressure,

parts and in the details can be made without departing from the principles of the invention or the scope of the claims.

WhatI claim is: 1. .In a carburetor, means providing an air intake passage, including a venturi for setting up diii'erential of air pressures proportional .to air flow, a fuel supply system including a constant :pressure pump, a main conduit for delivering fuel therefrom to a nozzle discharging into the air passage, a fixed metering restriction in said conduit, 'afuel pressure regulating device in the conduit intermediate the pumpnnd restriction including a valve for adjustably restricting said conduit, a'movable wall secured to the valve and having one side subjected to the pressure of said conduit upstream of the restriction thereby tending to clo e the valve, a restricted branch passage from ,the conduit downstream from the val e and arranged to subject the opposite side of said wall to a reduced pressure, said conduit extending to a second discharge nozzle in said air passage, and pressure responsive means subjected to said difierential of air pressures and to the fuel pressure in said branch passage to maintain fuel pressure in said branch passage proportional to said differential of air pressures, said regulating device having a spring arranged to urge the valve in an opening direction whereby said device maintains a fuel pressure upon said restriction greater thanthat in said branch and varying substantially as said differential of air pressures in accordance with air flow.

2. In a carburetor, means providing an air intake passage including a venturi for setting up differential of air pressures proportional to air flow, a fuel supply system including a constant pressure pump, a main conduit for delivering fuel therefrom to a nozzle discharging into the air passage, a fixed metering restriction in said conduit, a movable fuel-metering valve control-: ling aid conduit intermediate the pump and restriction, a wall secured to said valve, a casing enclosing said valve and wall and providing fluid pressure chambers at opposite sides of said wall subject normally to fuel pressures of different values, a spring assisting the action of the lower pressure on the valve and biasing the valve toward an open position, and means responsive to differential of air pressures in said intakepassage for effecting increases and decreases in the spring assisting fuel pressure, said last-named means including a branch conduit leading off from that side of the valve casing subject to the lower pressure and a valve located intermediate the ends of said last-named conduit for opening and closing the same, the terminal of said branch conduit located downstream of said last-named valve being arranged to deliver the vented fuel to the air intake passage.

3. In a fuel and airproportioning device for an internal combustion engine, air passagemeans for supplying air to the engine including a venturi for setting up differential of air pressures proportional to air flow, fuel supply means including a constant pressure pump, a metering orifice and a main conduit delivering to said orifice, a

conduit, said wall being operatively connected to said mainvalve for positioning the same, a restricted inlet passage connecting the interior of said chamber to said portion of said second conduit, a restricted outlet passage connecting the interior of said chamber to a point maintained at a continuously lower pressure, pilot valve means for controlling one of said restricted passages,

and means responsive to the difference of said air pressures for operating said pilot valve means.

5. A fuel-and air proportioning device for an internal vcombustion engine, comprising in combination; a first conduit for conveying air for combustion purposes to said engine, means associated with said first conduit for producing two unequal air pressures whose difference is a measure of the rate of flow of air thru said conduit,

means for supplying fuel under superatmospheric pressure, a second conduit for conveying fuel from said fuel supply means to said-engine.

' a metering restriction in said second conduit effective to control the flow of fuel therethru as a function of the fuel pressure differential thereacross, means for maintaining a substantially constant pressure in said conduit on one side of said restriction, a mainvalve in said second conduit on the opposite side of said restriction for variably restricting said second conduit to conmovable fuel-metering valve, a wall secured to said valve, a casing enclosing said valve and wall and located in said main conduit intermediate the pump and metering orifice and having a chamber at one side of said wall establishing fuel pressure on said valve in a closing direction, said casing also having a chamber at the opposite side of said wall providing a reduced fuel pressure on saidvalve in a valve-opening direction, a spring continuously assisting the action of said last-named pressure on the valve, and means controlled by differential of air pressures in said intake pas-- sage for'increasing and reducing the lower fuel pressure acting on the valve, the main conduit having an inlet to the high-pressure side of said casing and. an outlet from said side, and the side of said casing subject to the lower fuel pressure having a branch connection to the air passage means provided intermediate its ends with trol the pressure in the portion of said conduit between said valveand said restriction, an expansible chamber having a movable 'wall subject on its exterior surface to the fuel pressure in said portion of said second conduit, said wall being operatively connected to said main valve for positioning the same, a restricted inlet passage connecting the interior of said chamber to said portion of said second conduit, a restricted outlet passage connecting the interior of said chamber bustion engine, comprising a first conduit for conveying air for combustion purposes to said engine, means associated with said conduit for producing two unequal pressures whose difference is a measure of the quantity of air flowingtherethru, means for supplying fuel under superatmeans for opening and closing it as air-flow conditions in said passage means vary.

4. -A fuel and air proportioning device for an I internalcombustion engine, comprising in combination, a first conduit for conveying air for combustion purposes to said engine, 'means assoclated withsaid first conduit for producing two mospheric pressure, a second conduit for conveying fuel from said. fuel supply-means to said engine, a metering restriction in said second conduit, first valve means in said second conduit for 'variablyrestrlcting said second conduit to control the pressure therein between said valve means and said restriction, an expansible chamber having a movable wall subject onits exterior surmeans for supplying fuel under s'uperatmospheric 'pressure, a second conduit-for conveying fuel from said fuel supply means to said engine, a

metering restriction in said second conduit cfface to the fuel pressure in said portion of said second conduit, said wall being operatively connected to said first valve means for positioning the same, a restricted inlet passage connecting the interior of said chamber to said portion of said second conduit, a restricted outlet passage connecting the interior of said chamber to a point maintained at a continuously lower pressure, secand valve means for controlling one oi. said restricted passages, and. at least two flexible diaphragms operatively. connected to said second valve means, one of said diaphragms being subjected to said two unequal pressures, said one diaphragm being connected to said second valve 5 means so as to move said second valve means toward closed position when the diflerence of said unequal pressures increases, and the-second of said diaphragms being subjected to the pressure in said chamber and connected to said second valve means 'so as to move said second valve means toward open position when said third conduit pressure increases.

mm'on E. CHANDLER. 

